Independently rotatable detector plate for medical imaging device

ABSTRACT

A real-time fluoroscopic imaging system includes a collimator and a detector which are rotationally movable independent of the support assembly, e.g., c-arm, to which they are mounted. Rotational movement of the collimator and the detector are coordinated such that the orientation of the detector with respect to the collimator does not change. The collimator may include a geared flange member to facilitate rotation, and may be a single molded piece formed of a plastic such as tungsten polymer material. The system may also include a plurality of interchangeable collimators characterized by different shapes. A display is provided to present an image to an operator, and image orientation logic displays a target anatomy in a selected orientation regardless of orientation of the target anatomy relative to the detector, and regardless of rotation of the detector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application and claims priority under35 U.S.C. 120 to U.S. application Ser. No. 16/355,697 filed on Mar. 15,2019, which is a continuation application and claims priority under 35U.S.C. 120 to U.S. application Ser. No. 15/861,863 filed on Jan. 4, 2018(now U.S. Pat. No. 10,271,807 issued on Apr. 30, 2019), which is acontinuation of U.S. application Ser. No. 14/884,934 filed on Oct. 16,2015 (now U.S. Pat. No. 9,872,659 issued on Jan. 23, 2018), which is acontinuation of U.S. application Ser. No. 13/223,866 filed Sep. 1, 2011(now U.S. Pat. No. 9,161,727 issued on Oct. 20, 2015). The aboveapplications are hereby incorporated by reference in their entireties.

FIELD OF THE INVENTION

This invention relates generally to medical imaging, and moreparticularly to detector plates for medical imaging device.

BACKGROUND OF THE INVENTION

Real-time fluoroscopic imaging systems in which an x-ray emitter is in afixed relationship relative to an x-ray detector are in widespread use.The emitter and detector are typically mounted on opposing ends of aone-piece support assembly such as a C-shared arm. A variation known asa mini-C-arm is particularly useful for imaging extremities. Variousimprovements have been made since such imaging systems were initiallydeveloped. For example, the x-ray detector may include a digital x-rayflat-panel detector (FPO) with a complementary metal-oxide-semiconductor(“CMOS”) device. FPDs have better dynamic range and detection quantumefficiency (DQE) than previous detectors.

It is recognized that it is desirable to reposition the support assemblyto which the emitter and detector are mounted. For example, it may bedesirable to obtain a second, orthogonal view through the target whenrepairing a fracture or for implant placement. This can be accomplishedby either repositioning the support assembly or, alternatively, usingtwo imaging systems at right angles to one another. The support assemblymay be supported by a mechanism that enables rotation about an axis inorder to help orient the emitter and detector relative to the target Themechanism may be coupled to a cart or ceiling mount. Regardless of thetype of assembly used to fix the position of the emitter relative to thedetector, maintaining the relative positioning of the emitter relativeto the detector while enabling repositioning of the assembly facilitatesease of use.

SUMMARY OF THE INVENTION

The presently claimed invention is predicated in part on recognitionthat it may be desirable to re-orient a detector plate that produces anon-circular image. Previous amplifiers and detector plates might bemoved rotationally with the c-arm or other support assembly, but werenot equipped or required to move rotationally independent of the supportassembly because they were circular and produced a circular image, FPDsare typically rectangular in shape and produce a rectangular image.Further, the range of motion of a support assembly such as a c-an islimited. Consequently, it may be desirable to be able to rotate thedetector plate and amplifier independent of the support assembly.

In accordance with one non-limiting aspect of the invention an apparatuscomprises: an imaging device including an emitter, a collimator, adetector, and a support assembly, the collimator and detector beingmounted on the support assembly and being rotationally movableindependent of the support assembly.

In accordance with another non-limiting aspect of the invention a methodcomprises: rotating a detector and a collimator of an imaging deviceincluding an emitter and a support assembly, the collimator and detectorbeing mounted on the support assembly and being rotationally movedindependent of the support assembly; and providing an image of targetanatomy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the fluoroscopic imaging system.

FIG. 2 illustrates an embodiment of the fluoroscopic imaging system.

FIG. 3 is a block diagram of the scanner.

FIGS. 4, 5 and 6 illustrate the detector in greater detail.

FIGS. 7 and 8 illustrate the collimator in greater detail.

FIG. 9 illustrates an assembly for interchanging collimators.

FIG. 10 illustrates operation of the user interface in greater detail.

DETAILED DESCRIPTION

FIG. 1 is a block diagram of a fluoroscopic imaging system. The systemincludes a FPD 60, computer processing unit 62, user interface 66, andan x-ray source 64. The x-ray source and FPD operate to generate x-rayimages of a selected region of a patient's body. The computer processingunit 62 includes processing hardware and non-transitory computerreadable memory for controlling x-ray source 64 and processing x-rayimages obtained thereby under corresponding programming. Unit 62communicates interactively with a user interface 66. The actual physicalarrangement of system components may differ from the functionalillustration.

Referring now to FIG. 2, the imaging system includes an x-ray sourceassembly 30 and an image detector assembly 34, which can include a flatpanel detector (FPD). The x-ray source assembly and image detectorassembly are mounted on a mini C-arm assembly 24. The mini C-armassembly may be mounted to a mobile base 11 via an articulated anassembly 18 for supporting the mini C-Arm in a selected position. Thecomputer processing and a user interface (e.g., keyboard, monitor etc.)may also be mounted on the mobile base. The articulating arm assembly 18includes two arms 18 a and 18 b. The distal end of arm 18 b is connectedto a support arm assembly 20. The C-arm 24 is carried by the support armassembly 20 such that a track 28 of the C-arm is slidable within theC-arm locking mechanism. The x-ray source assembly 30 and x-ray detectorassembly 34 are respectively mounted at opposite extremities of theC-arm in facing relation to each other so that an x-ray beam 36 fromx-ray source assembly 30 impinges on the input end 38 of the detectorassembly 34. The x-ray source assembly 30 and detector end 38 are spacedapart by the C˜arm sufficiently to define a gap 40 between them, inwhich the limb or extremity of a human patient 42 can be inserted in thepath of the x-ray beam 36. The support arm assembly 20 connected to theend of arm 18 b provides 3-way pivotal mounting that enables the C-arm24 to be swiveled or rotated through 360° in each of three mutuallyperpendicular (x, y, z) planes and to be held stably at any desiredposition, while the arm 18 a of the articulating arm assembly 18 ismounted to the portable cabinet 11 at point “A” and jointed to enableits distal end and the C-arm to be angularly displaced both horizontallyand vertically. The multidirectional angular movability of the C-armassembly facilitates the positioning of the x-ray source and detectorassemblies in relation to a patient body portion to be irradiated.

Referring to FIGS. 2 and 3, the source assembly 30 includes an X-raysource 301, rotation mechanism 300, and collimator 22. Furthermore, thedetector assembly 34 includes a detector 303 and rotation mechanism 302.X-rays emitted by the x-ray source 301 are limited by the collimator 22into a distribution characterized by a selected shape. An x-ray filter310 is placed in the x-ray beam to eliminate variations in x-ray dosethat are inherent in the x-ray tube output. The collimated x-rays areprojected onto the image detector 303. An anatomical target, e.g., ahand or foot, is disposed between the source and the detector forimaging. The x-rays which pass through the target impinge on the x-raydetector, which produces raw x-ray data that is provided to the computerprocessing unit. The computer processing unit produces a set of pixelvalues for a projection image from the raw x-ray energy measurements.The pixel values are used to display an image on the interface.

The collimator 22 and detector 303 are rotationally movable independentof the c-arm. In other words, the collimator and detector can each berotated around an axis without moving the c-am1, which may includerotation of all or part of the source assembly 30 and detector assembly34. In one embodiment rotational movement of the collimator is enabledby coupling the collimator to the c-arm support assembly via rotationmechanism 300, and rotational movement of the detector is enabled bycoupling the detector to the c-arm support assembly via rotationmechanism 302. Previous amplifiers and detector plates were not equippedor required to move rotationally independent of the support assemblybecause they were circular and produced a circular image. FPDsassociated with the detector are typically rectangular in shape andproduce a rectangular image. Consequently, there is an advantage to thecollimator and detector being rotationally movable independent of thec-arm.

The rotational movement of the collimator, detector, and associatedrotation mechanisms are coordinated such that the orientation of thedetector with respect to the collimator does not change. For example,the rotation mechanism 300 associated with the collimator may beconfigured to match the rotation of the mechanism 302 associated withthe detector such that manual movement of the detector by the operatoris automatically mirrored by the collimator. Alternatively, oradditionally, the rotation mechanism associated with the detector may beconfigured to match the rotation of the mechanism associated with thecollimator such that movement of the collimator by the operator isautomatically mirrored by the detector. This may be accomplished with amechanical linkage, an electrical linkage, or any other suitablemechanism. In the illustrated embodiment the rotation mechanism. 302associated with the detector is coupled to a position sensor 304. As thedetector 303 is rotated, the position sensor 304 detects the rotationvia the rotation mechanism 302, and provides an indication of thedetected rotation to a control system 306. For example, the positionsensor may provide an indication of the rotational position of thedetector relative to a reference position, or alternatively anindication of change of position in terms such as rotational velocity(rotational speed and direction). The control system 306 operates toproduce a corresponding output which prompts the rotation mechanism 300associated with the collimator to rotate the collimator such thatrotation of the collimator matches rotation of the detector, e.g.,orientation of the detector with respect to the collimator does notchange. Consequently, when the operator rotates the detector, e.g.,manually or with controls, the collimator is automatically rotationallyrepositioned.

FIGS. 4 through 6 illustrate an embodiment of the detector 34 andassociated rotation mechanism 302 and position sensor 304 in greaterdetail. The detector 34 includes a rectangular FPD 400 mounted in achassis 402. The rotation mechanism 302 includes bearings 600 and achassis 602. The position sensor 304 may include an encoder 604 andcomparator 606. one of which is fixedly attached to the detector chassis402, e.g., with fasteners 608, the other of which is fixedly attached tothe rotation mechanism chassis. However, those skilled in the art willrecognize that any of a variety of alternative position sensors whichmay have different principles of operation.

FIGS. 7 and 8 illustrate an embodiment of the collimator 22 andassociated rotation mechanism 300 in greater detail. The collimator 22includes a geared flange member 700 and a central portion 702 thatdefines a frustum-shaped opening. The central portion is disposed in anopening of a base plate 704 such that the collimator is rotationallymovable relative to the base plate. A stepper motor 706 is mounted tothe base plate and coupled to the collimator via a gear 708, the teethof which engage the geared flange 700 of the collimator. The steppermotor 706 is coupled to the control system 306 (FIG. 3). Moreparticularly, the stepper motor operates in response to input from thecontrol system to cause the gear 708 to rotate, which in turn causes thecollimator to rotate due to engagement with the teeth of the flangemember 700. The magnitude and direction of the rotation are preciselycontrolled by the control system. Feedback may be provided to thecontrol system via a geared member 710 which engages the geared flangeportion 700. The geared member 710 may be coupled to a rotationalposition sensor 712.

At least the central portion 702 of the collimator 22 is constructedwith a material that is opaque to x-rays. In one embodiment thecollimator is a single molded piece (central portion and flange member)using a material that is impenetrable by x-rays but sufficientlynon-malleable and abrasion resistant that it is also suitable for thegear teeth. For example, and without limitation, the collimator may beformed from a plastic such as a tungsten polymer material. However, thecollimator may be an assembly with separate central portion and flangeparts, e.g., a dense and more malleable metallic central portion and aless dense and less malleable metallic flange. Alternatively, the flangemay be a multi-part assembly with the teeth formed from a materialhaving particular characteristics.

FIG. 9 illustrates a mechanism for selectably interchanging collimators702 a, 702 b. Two or more collimators are slidably mounted in series ina channel 900 of a base member 902. The collimators can be movedlinearly in two directions, thereby enabling a selected collimator to bemoved slidably into position relative to the detector 34 (FIG. 3). Thecollimators may be characterized by openings with various differentshapes. Consequently, the operator can easily reconfigure the imagingsystem to utilize a collimator having an opening with a desired shapeselected from a set of collimators mounted in the base without adding orremoving a collimator from the system. One or more sensors indicatewhich collimator is in position for active use. Information from thesensor may be provided to computer processing 62 (FIG. 1) in order tofacilitate image generation, processing and display. For example, thesource field from source 20 (FIG. 3) may be adjusted in response to thecollimator that is positioned for use.

FIG. 10 illustrates aspects of the computer processing 62 (FIG. 1) anduser interface 68 (FIG. 1) in greater detail. The user interfaceincludes a display 1000 for presenting an x-ray image to the operator.The computer processing controls presentation of the image on thedisplay such that it is de-coupled from orientation of the targetanatomy relative to the detector. Enabling the image to be displayedsuch that a particular orientation of the target anatomy as presentedallows the operator to, for example, view an image of a hand such as inFIG. 10A with the fingers pointing upward on the screen regardless ofhow the hand is oriented relative to the detector in corresponding FIG.10B. However, such orientation control is typically static once set, andin some cases a portion of the target that the operator wishes to viewmay not initially be within the field of the detector. In theillustrated example a fingertip and part of the wrist are not imaged inFIG. 10A because they are outside the field of view of the detector asshown in corresponding FIG. 10A. In order to move the portion of thetarget that is not being imaged into the field of view the target may bemoved. Alternatively, or additionally, the detector can be rotated asdescribed above. As shown in FIG. 10D the portions of the fingertip andwrist that were not imaged in FIG. 10B are imaged when the detector isrotated. However, the inventors have recognized that rotational movementof the detector and collimator could cause somewhat undesirable ordisorienting changes to the displayed image, particularly if thedetector is rotated during a medical procedure. In one embodiment thecomputer processing is coupled to the control system in order to monitorand react to rotational movement of the detector and collimator. Forexample, the computer processing may counter-rotate pixels of the imagerelative to the rotation of the detector such that the desiredorientation of the target is not changed when the detector andcollimator are rotated such as shown in FIG. 10C which corresponds toFIG. 10D. As a result, image orientation processing is dynamic, e.g.,maintaining an image of a hand with fingertips pointed upward regardlessof the position of the hand relative to the detector and also regardlessof rotation of the detector.

While the invention is described through the above exemplaryembodiments, it will be understood by those of ordinary skill in the artthat modification to and variation of the illustrated embodiments may bemade without departing from the inventive concepts herein disclosed.Moreover, while the preferred embodiments are described in connectionwith various illustrative structures, one skilled in the art willrecognize that the system. may be embodied using a variety of specificstructures.

Accordingly, the invention should not be viewed as limited except by thescope and spirit of the appended claims.

What is claimed is:
 1. A method of operating an X-ray imaging devicehaving an X-ray source assembly including an X-ray source and acollimator, and a detector separated by a gap from the X-ray source, themethod comprising: moving a position of the collimator relative to thedetector; automatically moving the detector from a position ofnon-alignment with the collimator to a position of alignment with thecollimator to match an orientation of the collimator; and obtaining animage of a patient's target anatomy.
 2. The method of claim 1, whereinmoving a position of the collimator relative to the detector comprisesmanually moving the collimator relative to the detector.
 3. The methodof claim 1, wherein moving a position of the collimator relative to thedetector and automatically moving the detector from a position ofnon-alignment with the collimator to a position of alignment with thecollimator to match an orientation of the collimator comprises: manuallymoving the collimator so that the orientation of the collimator ischanged relative to the detector; and automatically moving the detectorto re-align the orientation of the detector with the collimator tomaintain alignment of the orientation of the detector with thecollimator.
 4. The method of claim 1, further comprising: presenting theimage to an operator on a display; and displaying the patient's targetanatomy in a selected orientation regardless of an orientation of thepatient's target anatomy relative to the detector, and regardless of thedetector's position.
 5. The method of claim 5, wherein displaying thepatient's target anatomy comprises displaying the patient's targetanatomy placed between the collimator and the detector in real-time. 6.The method of claim 5, further comprising a processor arranged andconfigured to de-couple the selected orientation of the patient's targetanatomy relative to the detector, and wherein displaying the patient'starget anatomy in a selected orientation regardless of orientation ofthe patient's target anatomy relative to the detector comprises:dynamically adjusting the image of the patient's target anatomydisplayed on the display to maintain an orientation of the imageregardless of the detector's position.
 7. The method of claim 7, whereinthe processor is arranged and configured to counter-rotate pixels of theimage of the patient's target anatomy relative to the detector such thatthe orientation of the patient's target anatomy is not changed when thedetector and collimator are moved.
 8. The method of claim 1, wherein theX-ray imaging device further includes a C-arm support assembly, thecollimator and detector being mounted on opposite ends of the C-armsupport assembly in facing relation such that an emitted X-ray beam fromthe X-ray source impinges on an input end of the detector, thecollimator and detector being rotationally movable independent of theC-arm support assembly.
 9. The method of claim 8, wherein an axis ofrotation of the detector matches an axis of rotation of the collimator.10. The method of claim 9, wherein automatically moving the detectorfrom a position of non-alignment with the collimator to a position ofalignment with the collimator to match an orientation of the collimator;comprises: automatically rotating the detector to match the orientationof the collimator.
 11. The method of claim 1, wherein the X-ray imagingdevice further includes: a first position sensor arranged and configuredto determine a rotational position of the collimator; a second positionsensor arranged and configured to determine a rotational position of thedetector; and a control system arranged and configured to: control arotational position of the detector to mirror a rotational position ofthe collimator responsive to determining a change in the rotationalposition of the collimator.
 12. The method of claim 11, furthercomprising a rotation mechanism coupled to the detector, whereinautomatically moving the detector comprises: automatically moving thedetector via the rotation mechanism based on detecting a change in therotational position of the collimator using the first and secondposition sensors.
 13. The method of claim 12, wherein automaticallymoving the detector comprises: receiving an indication of detectedrotation of the collimator; and prompting, via the control system, therotation mechanism to rotate the detector so that rotation of thedetector matches rotation of the collimator.
 14. The method of claim 1,wherein the collimator includes a plurality of independent selectablecollimators, the method further comprises: selecting a desiredcollimator from the plurality of independent selectable collimators; andslidably moving the selected collimator into a position for use.
 15. Themethod of claim 1, wherein the collimator is positioned inside the X-raysource assembly and the X-ray source assembly is manually rotatable. 16.The method of claim 1, wherein the detector is a flat panel detector.17. The method of claim 1, wherein moving the collimator includesadjusting the shape of an aperture of the collimator.
 18. A method ofoperating an X-ray imaging device having an X-ray source assemblyincluding a collimator mounted on a first end of a support assembly anda detector mounted on a second end of the support assembly, the methodcomprising: emitting X-ray beams from the X-ray source to project ontothe detector, wherein the collimator is configured to shape the emittedbeams; adjusting the collimator within the X-ray source assembly from afirst configuration to a second configuration; and automaticallyorienting the detector to match an orientation of the collimator in thesecond configuration.
 19. The method of claim 18, wherein adjusting thecollimator comprises manually moving the collimator from the firstconfiguration to the second configuration.
 20. The method of claim 18,wherein the X-ray imaging device further includes a C-arm supportassembly, the X-ray source assembly and detector being mounted onopposite ends of the C-arm support assembly in facing relation such thatthe emitted X-ray beams from the X-ray source impinges on an input endof the detector, the collimator and detector being rotationally movableindependent of the C-arm support assembly.